A New Comet

Last weekend an amateur astronomer peered through
his telescope and found a new comet the old-fashioned way --
by looking.

August 24, 2001: In centuries
past astronomers discovered new comets the old-fashioned way:
they peered through telescopes or simply looked toward the sky,
hunting for faint smudges that no one had seen before. It was
hard work, but lots of people did it. Comets are named after
their discoverers, after all, and finding a new one can mean
instant fame. Hale-Bopp, Hayakutake and Shoemaker-Levy are just
a few of the names we know ... because of comets.

But lately it seems just about every new comet is called "LINEAR"
or "NEAT." Those are names, too, but not the names
of humans. They're robots -- automated, computer controlled telescopes
that scan the skies in a relentless search for near-Earth asteroids
and comets. This year between January and mid-August such telescopes
recorded 18 new comets, while humans had found none.

Above: Comet Petriew photographed on August 23rd by
Tim Puckett a using
a 60 cm Ritchey-Chretien reflecting telescope equipped with an
Apogee AP-7 CCD camera.

Comet hunters -- the human kind -- just can't compete! At
least that's how many beleaguered sky watchers have been feeling.
But last weekend an amateur proved humans can still bag a comet
and do it the old-fashioned way.

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Vance Petriew of Regina, Saskatchewan -- a computer consultant
by day and an amateur astronomer by night -- was at the Saskatchewan
Summer Star Party on August 18th when he turned his 20"
telescope toward the Crab Nebula. Hopping from one star to another
across the constellation Taurus, Petriew guided his telescope
toward the famous supernova remnant -- but he never made it.
He stopped instead at a curious smudge that appeared unexpectedly
in his eyepiece.

"I almost passed it by because I was looking for the
Crab Nebula," says Petriew, "and this wasn't it."
But there was something intriguing about the smudge, something
that made Petriew investigate further. "Thinking it might
be a galaxy, I looked at my star charts to see if any were nearby.
Just then Richard Huziak (Saskatoon Centre, Royal Astronomical
Society of Canada) happened to walk over for the first time that
night." Huziak was familiar with the region of sky and knew
that no eye-catching galaxy was in the vicinity. The pair quickly
realized that Petriew had stumbled onto an unknown comet.

"It's like winning the lottery!" says Petriew. "Only
[two people] in the whole world discovered a comet last year
the same way I did. It's pretty cool to have one named after
me and I'm very excited!"

Right: Vance poses with his 8 month old daughter
Emily and the 20" Obsession telescope he used to spot the
new comet.

Petriew announced his discovery hours later, and since then
astronomers have been monitoring the newfound comet to learn
more about it. Based on data spanning less that a week, it appears
that Comet Petriew may be traveling around the Sun once every
5.5 years following an elliptical path that stretches from a
point just inside Earth's orbit (0.95 AU) out to the realm of
the giant planet Jupiter (5.3 AU).

Says Brian Marsden of the Smithsonian Institution's Minor
Planet Center: "We're still not completely sure of the orbital
period, but Comet Petriew might have passed close to Jupiter
in 1982 -- an encounter that could have nudged the comet into
its current orbit." Before 1982 Comet Petriew's orbit was
probably bigger than it is now. It couldn't have come so close
to Earth in decades past, which might explain why it was never
spotted before.

Very long ago -- perhaps hundreds of millions of years --
Comet Petriew inhabited the Kuiper Belt, a doughnut-shaped cloud
of dormant comets that circle the Sun beyond Neptune. Kuiper
Belt comets tugged by the gravity of giant planets in the outer
solar system can be nudged closer to the Sun, where they might
eventually settle into orbits with periods of only a few years.
Comet Petriew appears to be one of these, a short period object
that will revisit the inner solar system frequently.

At the moment Comet Petriew is near perihelion, its closest
approach to the Sun. Solar heat is vaporizing the comet's icy
outer layers, unleashing a cloud of gas and dust around the nucleus.
That amorphous cloud, which astronomers call the "coma,"
is what caught Petriew's attention when he swung his telescope
through Taurus last Saturday. Photos captured since then reveal
a short tail, not much bigger than the coma itself. Seen through
modest telescopes Comet Petriew has the look of a cosmic tadpole.

Above: Comet Petriew is slowly gliding between the constellations
Taurus and Gemini, which appear in the eastern sky before dawn.
This star chart shows where to look on August 26, 2001. Click
to view orbital
elements, to calculate an ephemeris
for the comet, or to manipulate the comet's 3D
orbit. Vance Petriew has provided

, which shows the location of Comet Petriew every
day for a month beginning August 22, 2001.

"The comet should be around magnitude 10.5 this weekend,"
says Petriew. After that it will slowly fade as it recedes from
our planet, as well as from the Sun. If the comet is well-behaved,
it should remain brighter than 11th magnitude through mid-September.
"You will probably need a 6-inch telescope or larger to
see it," he added, "although a very keen observer might
spot it using a 4-inch."

No doubt plenty of astronomy enthusiasts will haul their telescopes
outdoors in the weeks ahead to peer at the new comet. And perhaps
some of them will scan the skies for comets of their own. It's
worth a try. After all, Vance Petriew is living proof that not
every comet's name is LINEAR.